The arithmographe “Ki Ser” is a small cylinder on which two mobile barems can be viewed simultaneously.

This arithmographe multiplies figures ranging from 15 to 95 with figures ranging from 100 to 1000.

To multiply 895 by 75, one rotates the sliding scale until 95 appears in the transparent window of 8 and refer to the intersection of column 75 and line 8. There are two numbers to add up: 600 (8×75) and 7,125. The addition of these two numbers taking into account their respective positions gives 67,125.

To facilitate its use by French merchants, figures are expressed in francs and centimes.